In dioceses of the fourth century and later, the archpriest was the head of a college of presbyters as special representative of the bishop. In larger rural localities or in extensive dioceses in the West, the term also refers to the head of the central mother-church or a diocesan subdivision or deanery. Union of several of either constituted an archidiaconate whose individual deans or archpriests were subject to the archdeacon. Over time this office has undergone a number of local changes and variations. Since the Council of Trent the duties of archpriest have been largely assumed by deans.